CHEM 2068 Laboratory Practical Review Sheet The laboratory practical is cumulati

Question

CHEM 2068 Laboratory Practical Review Sheet The laboratory practical is cumulative for the entire If you missed any labs, you responsible for the information covered during those labs. may bring one (1) three inch inch covered with any information you desire (front and back). Any cards larger than allowed size will be cut instructor You the Separation Scheme may bring one page with a copy of your or one has handwritten notes NOTES. An separation will be confiscated b your instructor before the exam. You may not use your separation Analysis report during the exam, so make sure you have a separate copy of your scheme for your use. You should know the following: and WHY) All techniques performed during the semester (how things are done The names and uses of all equipment (spelling the semester (refer to the "Glassware and that was distributed at the start of the semester) Definitions of important terms from the lab common chemicals used Chemical hazards and routes of chemical contamination for during the semester Laboratory safety rules How to use a Spec 20 structure affect physical properties somers: "cis" vs. trans"; how does isomer a catalyst; Isomerization: what is it; how did you accomplish what is the role of reaction coordinate diagram and how it relates to isomerization and catalysts Properties of liquids which ones were studied; how are they affected by physical environment (temperature, atmospheric pressure, etc); how to do calculations IMAF different types; how molecular structure affects lMAF calculate how are concentration and absorption related; how to Beer's Law: and properly use a calibration solution dilutions; how to construct color perception vs. wavelength absorbed item is derived Kinetics: rate what they mean and how each what the order zero, first and second order reactions how to determine data and usin of a reaction with respect to any substance involved using provided graphs relate to the order of the reaction and Kinetics: graphs: how do regression lines the rate constant Principle; effects of adding and removing Qualitative Equilibrium LeChatlier's reactants and products; effects of heating and cooling endothermic and exothermic Kea significance of relative values (greater than or less than 1.0) calculat Quantitative Equilibrium: How to calculate Keo; how to use ICE tables to Keg; what is the purpose of standard solutions; how to calculate concentrati dilutions weak acids; how to choose an indicator Acid/Base Titrations: strong acids vs. acid or monoprotic vs. diprotic acids; titration calculations; calculation of unknown base concentration using titration results systems Antacids: back titrations; calculations of back titrations; buffer CHEM 2068 Lab Practical Review Sheet Revised 6/2012

Explanation / Answer

Separation of ions in solution

Lets say we have two ions A2+ and B2+.

Adding NaCl, gives a precipitate of ACl2 and BCl2

ACl2 has a Ksp lower than Ksp of BCl2, that means initially when NaCl is added (low concentration), all of ACl2 will precipitate out of solution while BCl2 remins in dissolved form. When almost all of ACl2 is precipitates out, higher concentration of NaCl is added to precipitate out BCl2 from the solution. So Ksp tells us the solubility of salts and the concentration of precipitating agent can be adjusted to separated one ion over the other by selective precipitation of it over the other ion.

Lets say now we have Cu2+ and Ni2+ in a solution. If we pass H2S gas through the solution in acidic medium, CuS would precipitate out, while Ni2+ stays in solution. After basifying the solution, again H2S is passed and this time Ni2+ gets precipitated as NiS. So pH can be adjusted to separate ions in solution.

When we mix two solutions of say M^2+ and X^2- ions. The Qsp = [M^2+][X^2-] If is lower than Ksp for MX, then precipitation would not occur. We would get unsaturated solution. If Qsp > Ksp, precipitation would occur, this would be a saturated solution.

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